Caustic soda (sodium hydroxide, NaOH) and caustic potash (potassium hydroxide, KOH) are chemicals used to control the pH of water-based drilling fluids. Approximately 33,000 to 45,000 tons of these chemicals are used annually in the drilling fluids industry. Both are corrosive materials, handling of which causes injuries in the drilling industry each year. As used hereinafter the term “caustic” shall mean caustic soda, caustic potash, or a mixture of both chemicals. Before being added to the drilling fluid, dry caustic is dissolved in water at the drilling rig site. This process gives off a great deal of heat and results in a highly corrosive solution. Traditional methods of handling caustic at the drilling rig site involve the risk of exposure to dry caustic and concentrated caustic solutions resulting in severe burns and irritation to the skin, lung, and eyes.
Caustic used in drilling fluids is typically supplied to the rig in dry form (flakes or beads) in 40 lb or 50 lb sacks. While dry caustic is sometimes added directly to the drilling fluid system, more frequently it is dissolved in water at the rig site and added to the drilling fluid in liquid form to ensure that it is rapidly and evenly mixed throughout the entire drilling fluid system.
Several problems are encountered when dealing with sacks of caustic. First, empty sacks containing the dry powder residue are either improperly disposed of in land fills, or are incinerated. Next, back injuries result from lifting heavy sacks (40-50 lbs each) to pour in a mixing barrel. The mixing process requires a full protective hazmat suit, and all unprotected personnel must leave immediate area during this process. As a result of the wearing of the hazmat suit, the mobility and vision of personnel is limited. In addition, personnel turnover due to hazardous exposure is high. Finally, use of sacks can result in a lack of quality control in uniform mixing to fluid ratios.
To this end, a need exists for an improved caustic mixing apparatus and method which isolates personal at a work site from exposure to hazardous materials. It is to such an apparatus and method that the inventive concepts disclosed herein are directed.